SUNDAY, July 1 (HealthDay News) -- People who spend time outdoors during the summer should consider their heart health and take steps to avoid heat-related illnesses, says Dr. Alan Gertler, a cardiologist at the University of Alabama at Birmingham.

"The heat of summer increases stress on the heart, particularly during exercise," Gertler said in a university news release. "Exercise and the air temperature increase core body temperature, and high humidity further complicates the situation because sweat doesn't easily evaporate from your skin."

"Your body responds by diverting more blood to the skin to cool itself, which results in less blood flow to the muscles and consequently an increase in heart rate," Gertler continued.

"If you experience symptoms of heat-related illness while outdoors, stop what you're doing and get out of the heat," Gertler advised. "Drink plenty of fluids -- either water or a sports drink -- and remove extra clothing and wet down your body with cool water. If symptoms don't improve after 30 minutes -- or if you exhibit heat stroke symptoms -- seek medical attention immediately."

Heat-related illnesses are preventable, Gertler said. He offered the following tips to help people avoid these conditions while enjoying outdoor activities in the summer:

Hydrate. Drink 8 to 12 ounces of water 30 minutes before any type of physical activity. Drink 6 to 10 additional ounces for every 30 minutes of exercise. Drink sports drinks for any activities that last longer than an hour.

Get out early or late. Exercise early in the morning or in the evening, when temperatures are cooler.

Consider clothing. Choose light-colored, loose-fitting cotton T-shirts and shorts to stay cooler. Also wear a hat with a brim.

"Monitor your heart rate while you exercise, and stay within the range prescribed by your doctor," Gertler said. "If you have an underlying heart problem, talk to your doctor before exercising in the heat."